Conventional rotary drill bits, such as fixed cutter rotary drill bits for subterranean earth boring, have been employed for decades. It has been found that increasing the rotational speed of such drill bit attached to a drill string has, for a given weight on bit, increased the rate of penetration into the subterranean earth. However, increased rotational speed also has tended to decrease the life of the drill bit due to increased wear and damage of cutting elements mounted on the bit. The cutting elements most commonly employed are referred to as polycrystalline diamond compact (PDC) cutters, which comprise a diamond table formed on a supporting substrate of cemented carbide such as tungsten carbide (WC).
A conventional rotary drill bit comprises a bit body having a shank for connection of the drill bit to a drill string. Typically, the bit body contains an inner passageway for introducing drilling fluid pumped down a drill string to the face of the drill bit. The bit body is typically formed of steel or of a metal matrix including hard, wear-resistant particles, such as tungsten carbide infiltrated with a hardenable liquid copper alloy binder. Brazed into pockets within the bit body are PDC cutters that, together with nozzles for providing drilling fluid to the PDC cutters for cooling and lubrication, remove particles by shearing material from a subterranean formation when drilling. While the drilling fluid extends the life of the PDC cutters, the entrained particulates in the high flow rate drilling fluid comprised of solids in the fluid as well as formation cuttings may erode surfaces of the PDC cutters. Wear of surfaces on the PDC cutters may also be attributable to sliding contact of the PDC cutters with the formation being drilled under weight on bit, as well as by impact stresses caused by a phenomenon known as bit “whirl.” When the PDC cutters wear beyond a point where a large wear flat develops and the exposure of the PDC cutter above the surrounding bit face substantially reduces the depth of cut into the adjacent formation, their effectiveness in penetrating and cutting the subterranean formation is diminished, thus requiring repair and/or replacement of the PDC cutters. 
In order to appropriately replace and repair the worn or damaged PDC cutters that are brazed into the pockets of the bit body, the drill bit is often (if not always) returned to a repair facility qualified to repair the drill bit, resulting in lost utilization of the drill bit in terms both of time and revenue from drilling. The repair and/or replacement of PDC cutters is further complicated by the manufacturing process of brazing the PDC cutters into the pockets, which requires the controlled application of heat to de-braze and remove any worn and damaged PDC cutters without affecting other cutters on the bit, particularly those not needing repair, followed by brazing in replacement PDC cutters. Accordingly, there is a desire to provide a drill bit that accommodates wear by providing increased utilization of a cutting element in the form of a PDC cutter thereon without resorting to sending the drill bit to a repair facility. It is also desirable to facilitate field replacement of such cutting elements upon the bit body of a drill bit. In this regard, it is desirable to provide rotationally indexable cutting elements, which may be mechanically installed, removed and replaced, as well as drill bits configured for mounting such indexable cutting elements thereon.